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2324Re: [ai-geostats] Optimal rain gauge network

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  • Gerald van den Boogaart
    Jan 4, 2006
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      Dear Craig von Hagen,

      If you install a network of automated gauges, which is dense enough to make a
      map to check the manual gauges, sure enough it makes the manual network
      superfluous.

      And such network would not really help evaluating the operators:
      * Anyway if the measurement of a manual gauge is underestimated systematically
      by the interpolated surface I would first suspect a difference in
      microclimate to be the origin of that and not a bad operator.

      * If the variation of the measurement is underestimated by the kriging error I
      would suspect an additional measurment error in the manual measurements or a
      ill specified variogramm before blameing the operator.

      If you would like to check a manual network you might consider two options:

      1) Install mobile automatic gauges next to manual ones and check by simple
      comparison (however you need to consider wether the operator should be
      allowed to know that he is controlled currently). Than move the mobile gauge
      to the next station.

      2) To check single operators you can run cross-validation with the existing
      manual network: estimate a prediction and a kriging error from all stations
      but the one to be checked and compare. You need to add the nugget effect of
      the semivariogram to the kriging error to get the variance of
      Prediction-Measurement.

      Best regards,
      Gerald v.d. Boogaart




      Am Dienstag, 3. Januar 2006 14:53 schrieb Craig von Hagen:
      > Hi All,
      >
      > I have an interesting problem to solve, I hope
      > someone could help me.
      >
      > We are working on flood early warning in Somalia
      > and we have the following situation.
      >
      > We have an existing network of manual rain gauges
      > that we receive on a monthly basis with daily
      > readings taken manually by a person in the field.
      > These however can be unreliable.
      >
      > We have an option to install automatic rain gauges
      > that would give us an accurate measurement of
      > rainfall per day. We would like to use
      > geo-statistics to then give a prediction and error
      > surface and then use these surfaces to evaluate how
      > accurate and reliable our existing manual network
      > is.
      >
      > Is there a way to calculate the optimal network
      > (number and location) for the automatic stations so
      > that we get a reliable prediction surface which we
      > can then use to evaluate our manual network?
      >
      > I am the most familiar with the ArcGIS GeoStatistical
      > Analyst.
      >
      > Thanks and regards
      > Craig
      >
      >
      > Craig von Hagen
      > FAO - GLCN/Africover/SWALIM Projects
      > PO Box 30470-00100
      > Nairobi, Kenya
      >
      > Tel: +254 20 444 3331
      > Fax: +254 20 444 1993
      >
      > www.africover.org
      > www.glcn.org; www.glcn-lccs.org
      > www.faoswalim.org
      >
      >
      >
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      --
      -------------------------------------------------
      Prof. Dr. K. Gerald v.d. Boogaart
      Professor als Juniorprofessor fuer Statistik
      http://www.math-inf.uni-greifswald.de/statistik/

      office: Franz-Mehring-Str. 48, 1.Etage rechts
      e-mail: Gerald.Boogaart@...
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      paper-mail:
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      Institut f�r Mathematik und Informatik
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      Germany
      --------------------------------------------------
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